Mobile computing devices, such as a laptop or notebook PC, a smart phone, and tablet computing device, are now common tools used for producing, analyzing, communicating, and consuming data in both business and personal life. Consumers continue to embrace a mobile digital lifestyle as the ease of access to digital information increases with high speed wireless communications technologies becoming ubiquitous. Popular uses of mobile computing devices include displaying large amounts of high-resolution computer graphics information and video content, often wirelessly streamed to the device. While these devices typically include a display screen, the preferred visual experience of a high resolution, large format display cannot be easily replicated in such mobile devices because the physical size of such device is limited to promote mobility. Another drawback of the aforementioned device types is that the user interface is hands-dependent, typically requiring a user to enter data or make selections using a keyboard (physical or virtual) or touch-screen display. As a result, consumers are now seeking a hands-free, high quality, portable, color display solution to augment or replace their hands-dependent mobile devices.
Location awareness is increasingly important in many aspects of personal computing, especially those involving mobile devices. The standard way of obtaining location is to rely on GPS chipsets built into the device itself. However this only works reliably when the device has a clear line-of-sight view of the GPS satellites overhead. When operating indoors this is rarely the case, and GPS often fails to return an accurate position when within four walls. Several alternative indoor positioning methods exist, including inertial navigation and wireless beaconing. Inertial navigation uses accelerometers to track movement with respect to an initial position. Wireless beaconing uses fixed location wireless radio antennas (radio beacons) attached to structures, along with various forms of radio triangulation, to calculate exact or approximate mobile user position. Various wireless protocols may be used, for example WiFi, Cellular, and Bluetooth.
All of these indoor methods have limitations. Wireless beaconing requires extensive infrastructure to be set up and maintained.
The accelerometers used for inertial navigation have accuracy limitations, so that position calculations based on them suffer from “drift.” The longer time period over which inertial navigation (also referred to as dead reckoning navigation) is used, the more total “drift” is accumulated, which corresponds to error in the user's estimated location or position.
The state of the art approach to indoor navigation currently combines aspects of both wireless beaconing with accelerometer tracking Such a positioning device obtains an accurate fix of its indoor location by way of a short range wireless beacon. Once the fix is obtained, accelerometers try to keep the location estimate up to date as the device moves out of range of distributed, non-overlapping beacons.
Accelerometers may have a drift of about 5-10%. That means after walking around 100 feet following the last fix from a beacon, it is expected that that device's position estimate may be in error by +/−5 to 10 feet.